1. Field of the Invention
The present invention relates to an electron beam exposure apparatus and an electron beam exposure method, and, in particular, relates to a mask for multi-column electron beam exposure, the mask preferably being used for exposure using multiple column cells, and an electron beam exposure apparatus and an exposure method both using the mask.
2. Description of the Prior Art
In a conventional electron beam exposure apparatus, a stencil mask is provided with either a variable rectangular opening or multiple patterns, and the patterns are selected by beam deflection and transferred by exposure to a wafer. In such an electron beam exposure apparatus, although multiple mask patterns are provided, only a single electron beam is used for exposure. Accordingly, only one of the mask patterns is selected and transferred onto the wafer by the single electron beam at one time.
One of the exposure apparatuses having such a configuration is an electron beam exposure apparatus for partial one-shot exposure disclosed in, for example, Japanese Patent Application Laid-open Publication No. 2004-88071. The partial one-shot exposure is a technique used for transferring a pattern in the following steps in which: a region, for example 300 μm×300 μm, of a stencil pattern selected by beam deflection from multiple patterns, for example 100 pieces of patterns, arranged on a mask is irradiated with a beam; thereby the beam is formed to have a cross section shape of the selected stencil pattern; the beam having passed through the mask is deflected back by a deflector located in the subsequent stage; the beam is reduced at a certain reducing ratio, for example 1/10, determined by the configuration of an electron optical system; and then the pattern is transferred onto the surface of a sample wafer. The size of a region to be irradiated on the sample wafer is, for example, 5 μm×5 μm. In the partial one-shot exposure, if the stencil patterns are appropriately provided on the mask in accordance with a device pattern to be exposed, the number of necessary exposure shots can be largely reduced compared to the case where only a variable rectangular opening is provided on a mask. Accordingly, the throughput of exposure can be improved.
Meanwhile, a multi-column electron beam exposure apparatus is disclosed in Non-Patent document (see T. Haraguchi et. al., J. Vac. Sci. Technol, B22 (2004) 985). In the apparatus, an exposure process is performed by arranging, above a wafer, multiple column cells, each of which is equivalent to such a column of the exposure apparatus as described above but is in a smaller size, so that the multiple patterns can be transferred onto the wafer in parallel. Each of column cells is equivalent to a column in the single-column electron beam exposure apparatus; however, the throughput of the multi-column electron exposure can be increased by several times since the multiple patterns are transferred in parallel through the exposure process in the multi-column exposure system.
In the multi-column electron beam exposure apparatus, a stencil mask is mounted in each of the column cells for shaping the electron beam. Individual stencil masks are transferred by using a robot arm.
For example, in a multi-column electron beam exposure apparatus having 4 column cells in a 2×2 layout, it is easy to transfer stencil masks to be used in the respective column cells from outside of the column cells. However, when more column cells are provided, for example, in the case of a multi-column electron beam exposure apparatus having 16 column cells in a 4×4 layout, it is difficult to transfer stencil masks to be used in the 4 cells located in the middle.
In addition, in the case where different stencil masks are to be used in the column cells, it is necessary to provide a mask stage which can be independently driven in each of the column cells; thus, the structure becomes complicated. Furthermore, such a configuration will limit a movable range of the mask stages because they may interfere with each other when being driven.